Multiple Paleo-thermal Episodes in Mackenzie Corridor, Northwest Territory, Canada Revealed by Apatite Fission Track Analysis (AFTA): Implications for Hydrocarbon Prospectivity

Paul F. Green¹, Ian R. Duddy¹, Lee Slind², and Fred Rayer^2
1 Geotrack International Pty Ltd, Melbourne, Australia
² Alconsult International Ltd,

Approximately 250 exploration wells have been drilled and in the Mackenzie Corridor since the discovery of the Norman Wells oil field in 1920, with relatively few successes. Likely reasons include lack of understanding of potential sources, variation in maturation histories across the region, migration paths and availability of suitable traps at the time of migration, across this large and structurally complex area. AFTA (Apatite Fission Track Analysis) data in more than 20 wells from the region, integrated with organic maturity (vitrinite reflectance) data, has revealed multiple paleo-thermal episodes which exert significant control on maturation trends and hydrocarbon prospectivity, resolving some of these uncertainties. Over much of the region, Devonian units reached maximum maturities during the Jurassic, due to deep burial and elevated basal heat flow. Cooling began some time between 190 and 170 Ma, due to reduction in heat flow plus exhumation. Subsequent Early Cretaceous to Paleocene units were largely removed in two (or more) pulses of Cenozoic exhumation beginning in the intervals 60 to 40 Ma (Paleocene-Eocene) and 15 to 5 Ma (Mid-Late Miocene). But in certain areas, Early Cretaceous-Paleocene deposition was sufficient to heat underlying Devonian-Cambrian units to higher temperatures than those reached during the Jurassic, restarting source rock maturation from Devonian source rocks and resulting in a second phase of hydrocarbon generation during the Tertiary. We suggest that this style of history characterises the Norman Wells Field, illustrating how the later timing of maturation in such areas is more favourable for trapping and preservation of hydrocarbon accumulations.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005